TY  - JOUR
AU  - Rajić, Vladimir
AU  - Stojković-Simatović, Ivana
AU  - Veselinović, Ljiljana
AU  - Belosević-Cavor, Jelena
AU  - Novaković, Mirjana
AU  - Popović, Maja
AU  - Skapin, Sreco Davor
AU  - Mojović, Milos
AU  - Stojadinović, Stevan
AU  - Rac, Vladislav
AU  - Janković-Castvan, Ivona
AU  - Marković, Smilja
PY  - 2020
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5324
AB  - Eco-friendly and rapid microwave processing of a precipitate was used to produce Fe-doped zinc oxide (Zn1-xFexO,x= 0, 0.05, 0.1, 0.15 and 0.20; ZnO:Fe) nanoparticles, which were tested as catalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a moderately alkaline solution. The phase composition, crystal structure, morphology, textural properties, surface chemistry, optical properties and band structure were examined to comprehend the influence of Zn(2+)partial substitution with Fe(3+)on the catalytic activity of ZnO:Fe. Linear sweep voltammetry showed an improved catalytic activity of ZnO:5Fe toward the ORR, compared to pure ZnO, while with increased amounts of the Fe-dopant the activity decreased. The improvement was suggested by a more positive onset potential (0.394 Vvs.RHE), current density (0.231 mA cm(-2)at 0.150 Vvs.RHE), and faster kinetics (Tafel slope,b= 248 mV dec(-1)), and it may be due to the synergistic effect of (1) a sufficient amount of surface oxygen vacancies, and (2) a certain amount of plate-like particles composed of crystallites with well developed (0001) and (0001x304;) facets. Quite the contrary, the OER study showed that the introduction of Fe(3+)ions into the ZnO crystal structure resulted in enhanced catalytic activity of all ZnO:Fe samples, compared to pure ZnO, probably due to the modified binding energy and an optimized band structure. With the maximal current density of 1.066 mA cm(-2)at 2.216 Vvs.RHE, an onset potential of 1.856 Vvs.RHE, and the smallest potential difference between the OER and ORR (Delta E= 1.58 V), ZnO:10Fe may be considered a promising bifunctional catalyst toward the OER/ORR in moderately alkaline solution. This study demonstrates that the electrocatalytic activity of ZnO:Fe strongly depends on the defect chemistry and consequently the band structure. Along with providing fundamental insight into the electrocatalytic activity of ZnO:Fe, the study also indicates an optimal stoichiometry for enhanced bifunctional activity toward the OER/ORR, compared to pure ZnO.
PB  - Royal Soc Chemistry, Cambridge
T2  - Physical Chemistry Chemical Physics
T1  - Bifunctional catalytic activity of Zn1-xFexO toward the OER/ORR: seeking an optimal stoichiometry
EP  - 22095
IS  - 38
SP  - 22078
VL  - 22
DO  - 10.1039/d0cp03377d
ER  - 

@article{
author = "Rajić, Vladimir and Stojković-Simatović, Ivana and Veselinović, Ljiljana and Belosević-Cavor, Jelena and Novaković, Mirjana and Popović, Maja and Skapin, Sreco Davor and Mojović, Milos and Stojadinović, Stevan and Rac, Vladislav and Janković-Castvan, Ivona and Marković, Smilja",
year = "2020",
abstract = "Eco-friendly and rapid microwave processing of a precipitate was used to produce Fe-doped zinc oxide (Zn1-xFexO,x= 0, 0.05, 0.1, 0.15 and 0.20; ZnO:Fe) nanoparticles, which were tested as catalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a moderately alkaline solution. The phase composition, crystal structure, morphology, textural properties, surface chemistry, optical properties and band structure were examined to comprehend the influence of Zn(2+)partial substitution with Fe(3+)on the catalytic activity of ZnO:Fe. Linear sweep voltammetry showed an improved catalytic activity of ZnO:5Fe toward the ORR, compared to pure ZnO, while with increased amounts of the Fe-dopant the activity decreased. The improvement was suggested by a more positive onset potential (0.394 Vvs.RHE), current density (0.231 mA cm(-2)at 0.150 Vvs.RHE), and faster kinetics (Tafel slope,b= 248 mV dec(-1)), and it may be due to the synergistic effect of (1) a sufficient amount of surface oxygen vacancies, and (2) a certain amount of plate-like particles composed of crystallites with well developed (0001) and (0001x304;) facets. Quite the contrary, the OER study showed that the introduction of Fe(3+)ions into the ZnO crystal structure resulted in enhanced catalytic activity of all ZnO:Fe samples, compared to pure ZnO, probably due to the modified binding energy and an optimized band structure. With the maximal current density of 1.066 mA cm(-2)at 2.216 Vvs.RHE, an onset potential of 1.856 Vvs.RHE, and the smallest potential difference between the OER and ORR (Delta E= 1.58 V), ZnO:10Fe may be considered a promising bifunctional catalyst toward the OER/ORR in moderately alkaline solution. This study demonstrates that the electrocatalytic activity of ZnO:Fe strongly depends on the defect chemistry and consequently the band structure. Along with providing fundamental insight into the electrocatalytic activity of ZnO:Fe, the study also indicates an optimal stoichiometry for enhanced bifunctional activity toward the OER/ORR, compared to pure ZnO.",
publisher = "Royal Soc Chemistry, Cambridge",
journal = "Physical Chemistry Chemical Physics",
title = "Bifunctional catalytic activity of Zn1-xFexO toward the OER/ORR: seeking an optimal stoichiometry",
pages = "22095-22078",
number = "38",
volume = "22",
doi = "10.1039/d0cp03377d"
}

Rajić, V., Stojković-Simatović, I., Veselinović, L., Belosević-Cavor, J., Novaković, M., Popović, M., Skapin, S. D., Mojović, M., Stojadinović, S., Rac, V., Janković-Castvan, I.,& Marković, S.. (2020). Bifunctional catalytic activity of Zn1-xFexO toward the OER/ORR: seeking an optimal stoichiometry. in Physical Chemistry Chemical Physics
Royal Soc Chemistry, Cambridge., 22(38), 22078-22095.
https://doi.org/10.1039/d0cp03377d

Rajić V, Stojković-Simatović I, Veselinović L, Belosević-Cavor J, Novaković M, Popović M, Skapin SD, Mojović M, Stojadinović S, Rac V, Janković-Castvan I, Marković S. Bifunctional catalytic activity of Zn1-xFexO toward the OER/ORR: seeking an optimal stoichiometry. in Physical Chemistry Chemical Physics. 2020;22(38):22078-22095.
doi:10.1039/d0cp03377d .

Rajić, Vladimir, Stojković-Simatović, Ivana, Veselinović, Ljiljana, Belosević-Cavor, Jelena, Novaković, Mirjana, Popović, Maja, Skapin, Sreco Davor, Mojović, Milos, Stojadinović, Stevan, Rac, Vladislav, Janković-Castvan, Ivona, Marković, Smilja, "Bifunctional catalytic activity of Zn1-xFexO toward the OER/ORR: seeking an optimal stoichiometry" in Physical Chemistry Chemical Physics, 22, no. 38 (2020):22078-22095,
https://doi.org/10.1039/d0cp03377d . .

TY  - JOUR
AU  - Marković, Smilja
AU  - Stojković-Simatović, Ivana
AU  - Ahmetović, Sanita
AU  - Veselinović, Ljiljana
AU  - Stojadinović, Stevan
AU  - Rac, Vladislav
AU  - Skapin, Sreco Davor
AU  - Bajuk-Bogdanović, Danica
AU  - Janković-Castvan, Ivona
AU  - Uskoković, Dragan
PY  - 2019
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5091
AB  - ZnO nanopowders were produced using microwave processing of a precipitate and applied as a photoanode for photoelectrochemical water splitting. Two different surfactants, cetyltrimethylammonium bromide (CTAB) as the cationic and Pluronic F127 as the non-ionic one, were employed to in situ adjust the surface-to-bulk defect ratio in the ZnO crystal structure and further to modify the photo(electro)catalytic activity of the ZnO photoanode. The crystal structure, morphological, textural, optical and photo(electro)catalytic properties of ZnO particles were studied in detail to explain the profound effects of the surfactants on the photoanode activity. The ZnO/CTAB photoanode displayed the highest photocurrent density of 27 mA g(-1), compared to ZnO (10.4 mA g(-1)) and ZnO/F127 photoanodes (20 mA g(-1)) at 1.5 V vs. SCE in 0.1 M Na2SO4 under visible illumination of 90 mW cm(-2). A significant shift of the overpotential toward lower values was also observed when photoanodes were illuminated. The highest shift of the overpotential, from 1.296 to 0.248 V vs. SCE, was recorded when the ZnO/CTAB photanode was illuminated. The ZnO/CTAB photoanode provides efficient charge transfer across the electrode/electrolyte interface, with a longer lifetime of photogenerated electron-hole pairs and reduced possibility of charge recombination. The photoconversion efficiency was improved from 1.4% for ZnO and 0.9% for ZnO/F127 to 4.2% for ZnO/CTAB at 0.510 mV. A simple procedure for the synthesis of ZnO particles with improved photo(electro)catalytic properties was established and it was found that even a small amount of CTAB used during processing of ZnO increases the surface-to-bulk defect ratio. Optimization of the surface-to-bulk defect ratio in ZnO materials enables increase of the absorption capacity for visible light, rendering of the recombination rate of the photogenerated pair, as well as increase of both the photocurrent density and photoconversion efficiency.
PB  - Royal Soc Chemistry, Cambridge
T2  - RSC Advances
T1  - Surfactant-assisted microwave processing of ZnO particles: a simple way for designing the surface-to-bulk defect ratio and improving photo(electro)catalytic properties
EP  - 17178
IS  - 30
SP  - 17165
VL  - 9
DO  - 10.1039/c9ra02553g
ER  - 

@article{
author = "Marković, Smilja and Stojković-Simatović, Ivana and Ahmetović, Sanita and Veselinović, Ljiljana and Stojadinović, Stevan and Rac, Vladislav and Skapin, Sreco Davor and Bajuk-Bogdanović, Danica and Janković-Castvan, Ivona and Uskoković, Dragan",
year = "2019",
abstract = "ZnO nanopowders were produced using microwave processing of a precipitate and applied as a photoanode for photoelectrochemical water splitting. Two different surfactants, cetyltrimethylammonium bromide (CTAB) as the cationic and Pluronic F127 as the non-ionic one, were employed to in situ adjust the surface-to-bulk defect ratio in the ZnO crystal structure and further to modify the photo(electro)catalytic activity of the ZnO photoanode. The crystal structure, morphological, textural, optical and photo(electro)catalytic properties of ZnO particles were studied in detail to explain the profound effects of the surfactants on the photoanode activity. The ZnO/CTAB photoanode displayed the highest photocurrent density of 27 mA g(-1), compared to ZnO (10.4 mA g(-1)) and ZnO/F127 photoanodes (20 mA g(-1)) at 1.5 V vs. SCE in 0.1 M Na2SO4 under visible illumination of 90 mW cm(-2). A significant shift of the overpotential toward lower values was also observed when photoanodes were illuminated. The highest shift of the overpotential, from 1.296 to 0.248 V vs. SCE, was recorded when the ZnO/CTAB photanode was illuminated. The ZnO/CTAB photoanode provides efficient charge transfer across the electrode/electrolyte interface, with a longer lifetime of photogenerated electron-hole pairs and reduced possibility of charge recombination. The photoconversion efficiency was improved from 1.4% for ZnO and 0.9% for ZnO/F127 to 4.2% for ZnO/CTAB at 0.510 mV. A simple procedure for the synthesis of ZnO particles with improved photo(electro)catalytic properties was established and it was found that even a small amount of CTAB used during processing of ZnO increases the surface-to-bulk defect ratio. Optimization of the surface-to-bulk defect ratio in ZnO materials enables increase of the absorption capacity for visible light, rendering of the recombination rate of the photogenerated pair, as well as increase of both the photocurrent density and photoconversion efficiency.",
publisher = "Royal Soc Chemistry, Cambridge",
journal = "RSC Advances",
title = "Surfactant-assisted microwave processing of ZnO particles: a simple way for designing the surface-to-bulk defect ratio and improving photo(electro)catalytic properties",
pages = "17178-17165",
number = "30",
volume = "9",
doi = "10.1039/c9ra02553g"
}

Marković, S., Stojković-Simatović, I., Ahmetović, S., Veselinović, L., Stojadinović, S., Rac, V., Skapin, S. D., Bajuk-Bogdanović, D., Janković-Castvan, I.,& Uskoković, D.. (2019). Surfactant-assisted microwave processing of ZnO particles: a simple way for designing the surface-to-bulk defect ratio and improving photo(electro)catalytic properties. in RSC Advances
Royal Soc Chemistry, Cambridge., 9(30), 17165-17178.
https://doi.org/10.1039/c9ra02553g

Marković S, Stojković-Simatović I, Ahmetović S, Veselinović L, Stojadinović S, Rac V, Skapin SD, Bajuk-Bogdanović D, Janković-Castvan I, Uskoković D. Surfactant-assisted microwave processing of ZnO particles: a simple way for designing the surface-to-bulk defect ratio and improving photo(electro)catalytic properties. in RSC Advances. 2019;9(30):17165-17178.
doi:10.1039/c9ra02553g .

Marković, Smilja, Stojković-Simatović, Ivana, Ahmetović, Sanita, Veselinović, Ljiljana, Stojadinović, Stevan, Rac, Vladislav, Skapin, Sreco Davor, Bajuk-Bogdanović, Danica, Janković-Castvan, Ivona, Uskoković, Dragan, "Surfactant-assisted microwave processing of ZnO particles: a simple way for designing the surface-to-bulk defect ratio and improving photo(electro)catalytic properties" in RSC Advances, 9, no. 30 (2019):17165-17178,
https://doi.org/10.1039/c9ra02553g . .